1. Technical Field
This invention relates to grinding machines having improved dressing means and more particularly to two axis grinding machines having at least one grinding wheel with a complex shape.
2. Background Art
Angular feed grinding machines are well known in the art. U.S. Pat. No. 4,205,488 is exemplary of an angular feed grinding machine. Straight feed grinding machines are also well known in the art. U.S. Pat. No. 3,076,296 teaches a straight feed grinding machine.
U.S. Pat. No. 4,443,975 discloses and claims an external cylindrical grinding machine ("GRINDING CENTER") capable of straight and angular wheel feed. The grinding machine has a pair of independently driven grinding wheels mounted on a grinding wheel head assembly which can be swivelled to various stop points to bring either one of the wheels into position for grinding a workpiece. The Grinding Center includes a base which supports a swivel table, having a footstock and a driven work head mounted thereon, and a pair of flat longitudinally extending ways disposed behind the swivel table. A carriage is supported for movement along the longitudinal ways. The carriage is driven by a preloaded nut and ball screw arrangement powered by a servomotor. An incremental encoder, which is operable with the ball screw, provides information which is used for positioning the carriage. An elongated carriage traverse guide is provided substantially beneath the work piece location for guiding carriage movement and minimizing the effect of base thermal distortions. The carriage traverse guide permits the use of two flat ways for supporting the carriage. A pair of rearwardly extending ways, which support an upper wheel slide for back and forth movement relative to the swivel table, are provided on top of the carriage. The wheel head assembly is supported from the wheel slide for indexing movement about a pivot connection to bring either of the driven grinding wheels into position for grinding the workpiece.
The wheel slide is positioned with respect to the carriage by a preload nut and ball screw assembly which is driven by a servomotor. An incremental encoder, which is operable with the wheel slide ball screw, provides information which is used for positioning the wheel slide. The axis of movement of the wheel slide is orthogonal to the axis of movement of the carriage along the base.
The disclosed grinding center includes a computerized numerical control (CNC) controller having a programmable micro computer for controlling various machine functions. The carriage and wheel slide orthogonal feed axes can be selectively programmed to act independently or simultaneously, at independent or related feed rates, permitting use of the grinding machine as a straight plunge grinder or as an angle feed grinder. The disclosed machine is very versatile and can do work previously requiring two or three separate machines.
The simultaneous axes motion permits contour dressing and grinding of complex forms such as angles, radii, and chamfers. One of the principal advantages of applicant's present invention is the ability to quickly dress an altered or entirely new complex shape into the grinding wheel(s). Until applicant's invention, the dressing of complex shapes on a grinding wheel involved the use of a template arrangement, such as that taught in U.S. Pat. No. 2,900,974. Any change in the complex shape being dressed onto the grinding wheel involved a change of template, an operation generally taking up to 4 hours or more. With the dresssing apparatus of applicant's invention, this can now be achieved in a matter of a few minutes.